Increase bone integrity in laying hens

Each egg contains about 2g of calcium (Ca) in the form of calcium carbonate (CaCO3). The Ca needed to form the eggshell is coming from feed (60 – 75 %) and the bone (40 – 25 %). Ca from the bone is mobilized preferentially from the medullary, but also trabecular bone. The latter gives strength to the bone and cannot be repaired after Ca has been mobilized, which reduces bone strength and increases the risk for brittle bones. This leads to osteoporosis and increases the risk for fractures, for example in the keel bone.

Therefore, it is important to maximize Ca stores during rearing and minimise Ca mobilization from bone during laying. Another important factor is vitamin D3, which is a key player in Ca-metabolism. Vitamin D3 is needed not only to absorb Ca from the gut but also in concert with e.g. PTH to mobilize and restore Ca in bone, and to form the eggshell.

Keel bone damage (KBD), which includes keel bone deformations and keel bone fractures, has been reported to affect up to > 90 % of all birds in alternative housing systems, and the incidence depends on age and breed. KBD is a concern for animal welfare and reduces performance (http://www.keelbonedamage.eu/).

KBD is a multifactorial problem that needs to be addressed from different angles, especially because it increases with age, thus causing the hens to be kept longer every year. One was to achieve skeletal integrity is to provide sufficient Ca, supporting the vitamin D3 metabolism throughout the life of the laying hen.